1. Field of the Invention
This invention generally relates to a bicycle bottom bracket assembly. More specifically, the present invention relates to a bicycle bottom bracket assembly having bearings located within a cylindrical hanger part or bottom bracket tube of the bicycle frame.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle bottom bracket that is often called a bottom bracket.
Japanese Laid-Open Patent Publication No. 2004-249770 discloses a conventional bottom bracket that is mounted on a hanger part of a bicycle. The conventional bottom bracket is equipped with first and second bearing support members or housings that have first and second bearing retaining sections, respectively. The first and second axle support housings are screwed in to both end portions of the hanger part separately. The conventional crank axle assembly further includes first and second bearings that are stored on the first and second axle support housings. The crank axle is rotatably supported on both of the first and second bearings, and right and left cranks are non-rotatably mounted on the both axial end portions of the crank axle.
In such conventional bottom bracket, the right gear crank is secured on the right axial end portion of the crank axle. The inner rings of the first and second bearings are pressed by inner edge parts of the right and left cranks and disposed so that the right and left cranks can exert pressure to the inner rings of the first and second bearings. The left crank is non-rotatably mounted on the crank axle by a serration that is formed on a circumference surface at the left axial end portion of the crank axle. Moreover, the left crank is fastened to the crank axle by a fastening bolt that is screwed on the left edge inner circumference surface of the crank axle. When the left crank is fastened to the crank axle by the fastening bolt, the right and left cranks press the inner rings of the first and second bearings inwardly in the axial direction by placing the right and left cranks in contact with the outside surfaces of the inner rings of the first and second bearings in the axial direction. In addition, a slit is formed along the radial direction on a crank axle mounting part of the left crank. After fastening the left crank by the fastening bolt, the left crank can be further tightened securely on the crank axle by narrowing the width of the slit by using two mounting bolts. In the conventional bicycle bottom bracket as explained above, by pressing the inner rings of the first and second bearings by using the fastening bolt that secures the left crank, the bearing play is adjusted through the left crank by fastening the left crank to the crank axle. Then, the left crank is further secured onto the crank axle by narrowing the width of the slit of the left crank by the mounting bolts.
However, in this type of conventional bicycle bottom bracket, the bearings are located outside of the cylindrical hanger part or bottom bracket tube of the bicycle frame. As a result, the axial length of the bottom bracket tube of the bicycle frame needs to be made small enough to accommodate the bearings being located outside of the bottom bracket tube of the bicycle frame. Moreover, since the first and second axle support housings are screwed into the bottom bracket tube of the bicycle frame, the first and second axle support housings are made of a metallic material and the ends of the bottom bracket tube are threaded. Thus, this conventional bicycle bottom bracket structure can be heavy and requires threading of the ends of the bottom bracket tube.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle crank axle bearing assembly or bottom bracket. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.